scholarly journals Solidification performances of contaminants by red mud-based cementitious paste filling material and leaching behavior of contaminants in different pH and redox potential environments

Author(s):  
Yue Zhao ◽  
Yun Zhang ◽  
Zhihuai Zhao ◽  
Xuefeng Ma ◽  
Yun Cai

Abstract Considering the urgent need for disposal of red mud and the comprehensive treatment of coal mined-out areas, this paper presented red mud-based cementitious paste filling material (RMFM) to achieve the purpose of green filling treatment. However, the solidification performance of alkaline RMFM for contaminants can be affected when in contact with acid goaf water in practice, which may in turn causes secondary pollution to the surroundings. The leaching tests of RMFM under different pH and redox potential (Eh) conditions were designed to investigate the effects of environmental elements on the solidification performance of RMFM, and primarily investigated the treatment effectiveness of RMFM on goaf water. The test results manifest that the acidic and oxidizing environments could damage the hydration products generated by alkali and sulfate activation, thus affecting the solidification performance, while the alkaline and reducing environments could effectively prevent the release of the contaminants by enhancing the degree of alkali activation and inhibiting oxidation acid forming process. In the possible exposure environment, RMFM could effectively stabilize its own pollutants without secondary pollution. In addition, the powder RMFM samples had significant removal effects on heavy metals, the values of Cu, Pb, and As removal efficiency all reached more than 96.15%.

2016 ◽  
Vol 866 ◽  
pp. 99-105 ◽  
Author(s):  
Smita Singh ◽  
M.U. Aswath ◽  
R.V. Ranganath

The present investigation is on the effect of red mud on the mechanical properties and durability of the geopolymer paste in sulphuric and acetic acid solution. Red mud and fly ash were used to form the geopolymer paste along with the alkalies. The variation of red mud in the paste composition was from 0% to 90%. Cylindrical shaped specimens of 1 inch diameter and 1 inch height were prepared. The specimens were immersed in 5% sulphuric acid and 5% acetic acid for 1, 7, 14, 28, 56 and 84 days and tested for weight loss, visual deformation, strength loss and colour of the solvent, based on the procedure specified by ASTM C 267 – 01. SEM/EDX Tests were performed on the geopolymer specimens. Test results show that initially, the strength of the geopolymer increased upon the addition of red mud. The strength was maximum when the percentage of red mud was 30%. The maximum strength obtained was 38 MPa for the paste containing 30% red mud using 10M alkali solution as against 31.69 MPa, when only fly ash was used. Geopolymer paste containing 30% and 50% red mud showed better resistance to acid attack. The strength loss was minimum for the samples containing 30% red mud in both inorganic and organic acid i.e. sulphuric and acetic acid.


Author(s):  
Kang Zhao ◽  
Jucun Huang ◽  
Dan Dai ◽  
Yuwei Feng ◽  
Liming Liu ◽  
...  

AbstractWe report a case of acute myelitis in a patient infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A 66-year-old man with coronavirus disease 2019 was admitted with acute flaccid paralysis of the bilateral lower limbs and urinary and bowel incontinence. All serum microbiological test results were negative, except for SARS-CoV-2 nucleic acid testing. Clinical findings indicated post-infectious acute myelitis. He received treatment containing ganciclovir, lopinavir/ritonavir, moxifloxacin, dexamethasone, human immunoglobulin, and mecobalamin. With a diagnosis of post-infectious acute myelitis and comprehensive treatment, paralysis of the bilateral lower extremities ameliorated. After two negative novel coronavirus RNA nasopharyngeal swab tests, he was discharged and transferred to a designated hospital for isolation and rehabilitation therapy.


2018 ◽  
Vol 385 ◽  
pp. 391-396
Author(s):  
Mei Ling Guo ◽  
Ming Jen Tan ◽  
Xu Song ◽  
Beng Wah Chua

Hybrid superplastic forming (SPF) is a novel sheet metal forming technique that combines hot drawing with gas forming process. Compared with the conventional SPF process, the thickness distribution of AZ31B part formed by this hybrid SPF method has been significantly improved. Additionally, the microstructure evolution of AZ31 was examined by electron backscatter diffraction (EBSD). Many subgrains with low misorientation angle were observed in the coarse grains during SPF. Based on the tensile test results, parameters of hyperbolic sine creep law model was determined at 400 oC. The hybrid SPF behavior of non-superplastic grade AZ31B was predicted by ABAQUS using this material forming model. The FEM results of thickness distribution, thinning characteristics and forming height were compared with the experimental results and have shown reasonable agreement with each other.


2015 ◽  
Vol 03 (02) ◽  
pp. 071-079
Author(s):  
Rajender Singh ◽  
Ashu Gupta ◽  
Vishal Sharma

Abstract Objectives: This study was undertaken to evaluate the efficiency of two rotary nickel titanium instruments and hand instrumentation in removing gutta-percha and sealer from root canals. Study design: – 63 extracted human single rooted premolars were instrumented with K-files and filled using lateral compaction of gutta-percha (GP) and three different sealers. The teeth were randomly divided into three experimental groups of 21 specimens each. Removal of gutta-percha was performed with R-Endo retreatment files, Mtwo retreatment files and Hedstrom files. Time to reach working length and to eliminate filling material was also recorded. The specimens were sectioned for evaluation of the area of the remaining gutta-percha/sealer under stereomicroscope at 6X magnification. Photographs were taken for further analysis using computer image analysis program. The results were statistically analyzed using Analysis of variance (ANOVA) and Tukey’s honestly significant difference test. Results: The R-Endo retreatment system resulted in a smaller percentage of canal area covered by residual GP/sealer than in other groups, a significant difference was found between R-Endo and Mtwo group and between Hedstrom groups (P < 0.001). The Mean operating time was minimum with R-Endo group while it was found to be maximum with hand files. Conclusion: It was concluded that all test techniques left gutta-percha/sealer remnants within the root canal. The R-Endo retreatment files and Mtwo retreatment files system proved to be an efficient method for removing gutta-percha and sealer from single rooted premolars.


2012 ◽  
Vol 430-432 ◽  
pp. 539-542 ◽  
Author(s):  
Ho Sung Lee ◽  
Jong Hoon Yoon ◽  
Joon Tae Yoo

By using biaxial bulge test, it is possible to predict sheet metal forming behavior during hot forming process. The purpose of this study is to obtain materials parameters for elevated temperature forming condition during biaxial bulge test of a nickel base superalloy in hemispherical die. At constant gas pressure, the strain rate in which the metal sheet experiences varies and therefore the strain rate sensitivity can be obtained in a single loading. Biaxial bulge tests on superalloy metal sheet were performed and results are in satisfactory agreement with uniaxial test results at elevated temperature.


2017 ◽  
Vol 744 ◽  
pp. 254-258
Author(s):  
Jung Han Song ◽  
Injea Jang ◽  
Suh Yun Gwak ◽  
Jun Ho Bang ◽  
Yong Bae Kim ◽  
...  

In this study, the electric current effects in the deformation of light weight alloys are investigated to improve the formability. To begin with, a test system is built up to carry out the tensile test with heavy electric current flowing through the specimen. The evolutions of the flow stresses and failure elongations were obtained using this test system. The thermal and athermal effect such as electro-plastic effect of metallic materials induced by high density current make significant reduction of the flow stress, which is beneficial to the forming process of less formable metal. From the uniaxial test results, pulse current-assisted deep drawing test were conducted. The experimental results demonstrate that electrically assisted warm forming provides lower energy consumption and higher efficiency.


1993 ◽  
Vol 333 ◽  
Author(s):  
Tsuyoshi Imakita ◽  
Kaoru Sasakawa ◽  
Fumio Matsuda ◽  
Ryutaro Wada

ABSTRACTA corrosion test of a model waste glass was carried out with and without carbon steel, and the leaching behavior of the glass was studied under reducing condition in a glove box purged with N2. The redox potential and pH were monitored, and the concentration of Fe, Na, Si, and Mo in the leachates were measured to understand the leaching behavior of the glass. The redox potential of the leachates obtained in the corrosion test coexisting with carbon steel under reducing conditions showed initially that it was based on an Fe0/Fe2+ redox potential, and gradually it increased to that based on Fe2+/Fe3+ one. The corrosion rate of the glass under oxidizing conditions was ten times greater than that obtained with carbon steel, and that under reducing condition with carbon steel was negligible small.


Author(s):  
Kovalyshyn O. A.

The reproductive system is exposed to various adverse factors and harmful effects at all stages of functioning of an organism. Against the background of declining levels of women's reproductive health in recent years, there has been a clear tendency towards an increase in the number of patients with pathology of puberty. The low level of somatic and reproductive health before pregnancy causes a high incidence of complicated labors, which leads to a deterioration in the development of subsequent generations.The purpose of the study. To provide clinical characteristics of women who had menstrual dysfunction in puberty, which were based on the study of clinical and anamnestic data, laboratory and instrumental research methods, analysis of risk factors, clinical course, treatment effectiveness and dispensary observation.Materials and methods. According to the nature of the disfunctions, the main group of women (n = 210) who had menstrual disorders in puberty was divided into 3 subgroups (n = 70): the first - women with primary oligomenorrhea and timely average menarche, the second - with late menarche, the third - with pubertal bleeding. The control group included women (n = 70) with the correct rhythm of menstruation in puberty.Results. The clinical prospective study analyzed the social status of women with reproductive dysfunction in puberty, the frequency and structure of existing concomitant somatic diseases, the duration of the menstrual cycle, the nature of diseases of the female genital organs; the assessment of the comprehensive treatment of revealed disorders, which allowed to obtain a favorable reproductive prognosis. The majority of surveyed women (53.3%) planned a pregnancy, which occurred in 75.9% from among of planning ones.Conclusions. The conduction of clinical and anamnestic analysis of the reproductive function of women with menstrual dysfunction in puberty will increase the effectiveness of the treatment of identified disorders and will allow developing algorithms for management of such women during planning and during pregnancy.


2012 ◽  
Vol 66 (5) ◽  
pp. 781-786 ◽  
Author(s):  
Damir Barbir ◽  
Pero Dabic ◽  
Petar Krolo

This study has examined leaching behavior of monolithic stabilized/solidified products contaminated with zinc by performing modified dynamic leaching test. The effectiveness of cement-based stabilization/solidification treatment was evaluated by determining the cumulative release of Zn and diffusion coefficients, De. The experimental results indicated that the cumulative release of Zn decreases as the addition of binder increases. The values of the Zn diffusion coefficients for all samples ranged from 1.210-8 to 1.1610-12 cm2 s-1. The samples with higher amounts of binder had lower De values. The test results showed that cement-based stabilization/solidification treatment was effective in immobilization of electroplating sludge and waste zeolite. A model developed by de Groot and van der Sloot was used to clarify the controlling mechanisms. The controlling leaching mechanism was found to be diffusion for samples with small amounts of waste material, and dissolution for higher waste contents.


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